We have recently shown that bridging of IgE-receptors on mast cells, either by divalent anti-receptor antibody or by IgE and anti-IgE induced activation of methyl-transferases at the membrane, and that phospholipid methylation set a stage leading to opening Ca ion channels and histamine release. In the next fiscal year, 1) we shall study to learn whether phospholipid methylation is controlled by intracellular cyclic AMP. 2) In view of previous findings that intracellular cyclic AMP level tentatively increases immediately after bridging of cell-bound IgE, experiments will be carried out to study the relationship between phospholipid methylation and cyclic AMP response. 3) Based on evidence that protease or serine-esterase may be involved in mediator release from mast cells, possible relationship between protease and methyltransferases will be investigated.